The present invention relates generally to printheads, and more particularly to joining of different materials of a carrier for printhead dies in a printhead assembly.
A conventional inkjet printing system includes a printhead, an ink supply which supplies liquid ink to the printhead, and an electronic controller which controls the printhead. The printhead ejects ink drops through a plurality of orifices or nozzles and toward a print medium, such as a sheet of paper, so as to print onto the print medium. Typically, the orifices are arranged in one or more arrays such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other.
In one arrangement, commonly referred to as a wide-array inkjet printing system, a plurality of individual printheads, also referred to as printhead dies, are mounted on a single carrier. As such, a number of nozzles and, therefore, an overall number of ink drops which can be ejected per second is increased. Since the overall number of drops which can be ejected per second is increased, printing speed can be increased with the wide-array inkjet printing system.
Mounting a plurality of printhead dies on a single carrier, however, requires that the single carrier perform several functions including fluid and electrical routing as well as printhead die support. More specifically, the single carrier must accommodate communication of ink between the ink supply and each of the printhead dies, accommodate communication of electrical signals between the electronic controller and each of the printhead dies, and provide a stable support for each of the printhead dies. Unfortunately, effectively combining these functions in one unitary structure is difficult.
To effectively combine the functions of fluid and electrical routing and printhead die support, the single carrier may include multiple components each formed of different materials and joined or assembled together to create the single carrier. As such, the various components may have different coefficients of thermal expansion. Thus, joints between the various components must withstand high temperatures and/or temperature variations during operation of the printing system as well as stresses such as normal and/or peeling stresses between the components. In addition, the joints must also compensate for surface variations between the components.
One aspect of the present invention provides a carrier for a plurality of fluid ejection devices. The carrier includes a substrate and a substructure. The substrate includes a first material and has a first side adapted to receive the fluid ejection devices and a second side opposite the first side, and the substructure is formed of a second material and joined to the second side of the substrate with a lap joint. The lap joint includes a first portion formed by a portion of one of the substrate and the substructure, a second portion formed by a portion of the other of the substrate and the substructure, and a third material interposed between the first portion and the second portion.